PL213852B1 - Transparent ohm contact and production method of transparent ohm contact - Google Patents

Description

Description of the invention

The present invention relates to a transparent ohmic contact, in particular a low-resistance p-type ohmic contact for GaSb-based devices operating in the mid-infrared range, and a method of producing this contact. The contact according to the invention is made of transparent conductive oxides, especially indicated for photovoltaic and thermophotovoltaic devices.

Photodetectors and thermophotovoltaic cells are a group of devices for which transparent ohmic contacts acting as electrodes are of particular importance. While in the case of solar cells the use of transparent and conductive electrodes is widely described, few studies inform about transparent oxide electrodes for devices working in the mid-infrared range, in which the active layers are InxGa1-xAsySb1-y quadruple compounds matched to GaSb.

In photovoltaic devices, the contact electrode is placed on the front photosensitive surface, and in known solutions, the seemingly subtle grid pattern of the electrical contact covers up to 15% of the active surface of the detector, which significantly reduces the detectability of these devices.

The use of a transparent electrode allows for the maximization of the active surface, which in the case of detectors increases the R0A parameter of the detector and, consequently, improves its detectability.

Materials used as transparent electrodes in optoelectronic devices operating in the visible and near infrared range, such as indium tin oxide (ITO), have an increasing value of absorption and reflection in the mid-infrared range. Thus, their use in instruments working in this range is limited. Therefore, in the case of GaSb-based semiconductors, indium tin oxide is not applicable.

The object of the invention is to provide a transparent and low-resistance p-type contact as an electrode for GaSb-based semiconductor devices operating in the mid-infrared range and a method of producing this contact.

The transparent ohmic contact according to the invention is a conductive meta-3 oxide layer with a thickness of 50 - 100 nm and a resistance of less than 1x10 'Qcm and a transmittance of more than 85% in the spectral range of 1.8 - 2.4. p.

The method of producing a contact according to the invention consists in that a transparent, conductive metal oxide layer 50-100 nm thick is applied to the highly doped p-type sub-contact layer, preferably by sputtering.

A layer of cadmium oxide can be applied to the highly doped p-type sub-contact layer by means of reactive magnetron sputtering from a metal target Cd.

CdO. In this case, the application of this layer is carried out in a 1:10 mixture of oxygen and argon, with a generator power of 50 W and an argon pressure (pAr) of 1x10 ^-2 mbar.

A layer of RuSiO4 ruthenium silicon oxide can be applied to the highly doped p-type sub-contact layer by means of reactive magnetron sputtering from the metal target Ru1Si1. In this case, the application of the layer takes place in a mixture of oxygen and argon in a ratio of 1: 5, with the generator power of 100 W and an argon pressure (Pr) 5x10 ^-3 mbar. A zinc oxide layer of ZnO can be applied to the highly doped p-type sub-contact layer by magnetron sputtering from a ZnO target. In this case, the application of the war-3 stwy takes place in a fashion RF cathode at a current of 160 mA and argon pressure (Pr) 2x10 ^-3 mbar.

The contact according to the invention has more than 85% transmission in the mid-infrared range. The method according to the invention makes it possible to create a low-resistance ohmic contact immediately after deposition, without the need for additional thermal processes.

The invention will be explained in more detail on the examples of three different transparent and conductive electrodes made on the heterostructure of the GaSb / In (Al) GaSb semiconductor detector.

The exemplary heterostructure has four areas: substrate with nz GaSb conductivity with crystallographic orientation (100) and network-matched layers of quadruple compounds: narrow-gap n-In0.19Ga0.81As0.16Sb0.84 (base) and p-In0.19Ga0.81As0 layers. 16Sb0.84 (emitter) and

The wide-gap highly doped window layer p-Al0.21Ga0.79As0.02Sb0.98, which is also a sub-contact layer.

In the first exemplary solution, a CdO (cadmium oxide) electrode with a thickness of 50 nm was applied to such a heterostructure by means of reactive direct current sputtering, the deposition process was carried out from a cadmium target, in an atmosphere consisting of a mixture of oxygen -2 and argon in the proportion O2 / Ar = 10% , at generator power P = 50 W and argon pressure pAr = 1x10 ^-2 mbar. In the second exemplary solution, a ZnO (zinc oxide) electrode with a thickness of 50 nm was applied to the identical heterostructure by the method of high-frequency cathode sputtering, and the process was carried out in an argon atmosphere from a zinc oxide target, at cathode current Ic = 160 mA and total pressure pAr = 2x ^10-3 mbar.

In the third example, by the method of reactive DC sputtering, a RuSiO4 electrode (ruthenium-silica) with a thickness of 50 nm was applied to the described heterostructure, and the deposition was carried out in a mixture of oxygen and argon in the proportion O2 / Ar = 20%, from a ruthenium-3 silicon target at generator power P = 100 W and argon pressure pAr = 5x10 ^-3 mbar.

Claims (5)

1. Transparent ohmic contact for semiconductor devices made of quadruple compounds network-matched to GaSb, working in the mid-infrared range, characterized by the fact that it is a conductive metal oxide layer with a thickness of 50 - 100 nm and resistance less than 1x10 ^- Qcm and transmittance above 85% in the spectral range of 1.8 - 2.4 μm, located on the highly doped p-type sub-contact layer. 2. A method for producing a transparent ohmic contact for semiconductor devices from GaSb cross-matched quad compounds operating in the mid-infrared range, characterized in that a layer of transparent, conductive metal oxide with a thickness of 50 - 100 nm. 3. The method according to p. The method of claim 2, characterized in that a layer of cadmium oxide CdO is applied to the highly doped p-type sub-contact layer by means of reactive magnetron sputtering from a metal target CdO, the layer being deposited in a 1:10 mixture of oxygen and argon, with a generator power of 50 W and at argon pressure (pAr) 1x10 ^-2 mbar. 4. The method according to p. 2. The method of claim 2, characterized in that the highly doped p-type sub-contact layer by means of reactive magnetron sputtering from a metal target Ru1Si1 applied to the silicon oxide layer rutenowo RuSiO4, wherein applying the layer is performed in a mixture of oxygen and argon in a ratio of 1: 5, with the generator power of 100 W, and pressure of argon -3 (PAR) 5x10 ^-3 mbar. 5. The method according to p. 2. The method of claim 2, characterized in that a ZnO layer of zinc oxide is deposited on the highly doped p-type sub-contact layer by means of magnetron sputtering from a ZnO target, the layer being deposited in the RF mode at the cathode current -3 160 mA and argon pressure (Pr) 2x10 ^-3 mbar.